Polypropylene resin composition

ABSTRACT

Disclosed is a polypropylene resin composition including from 50 to 93% by weight of polypropylene resin including propylene-ethylene block copolymer satisfying given requirements, from 1 to 25% by weight of ethylene-α-olefin copolymer rubber made up of ethylene units and units of C 4-12  α-olefin having a density of 0.850 to 0.870 g/cm 3  and an MFR of 0.05 to 1 g/10 min, from 1 to 25% by weight of another type of ethylene-α-olefin copolymer rubber made up of ethylene units and units of C 4-12  α-olefin having a density of 0.850 to 0.870 g/cm2 and an MFR of 2 to 20 g/10 min, and from 5 to 25% by weight of inorganic filler. Molded articles made from the composition have good balance between rigidity and impact resistance and have good appearance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polypropylene resin compositions and toinjection molded articles made therefrom. In particular, the inventionrelates to a polypropylene resin composition which has superior fluidityand which is useful as a raw material of molded articles having goodbalance between rigidity and impact resistance and having, if any, anunnoticeable weld line, and to a molded article made therefrom.

2. Description of the Related Art

Polypropylene resin compositions are materials excellent in rigidity,impact resistance, etc. and therefore are used for a wide variety ofapplications in the form, for example, of automotive interior orexterior components and housings of electric appliances.

For example, JP9-71711 A discloses a propylene-based resin compositionwhich includes a propylene-ethylene block copolymer including acrystalline propylene homopolymer portion and an ethylene-propylenerandom copolymer portion having an ethylene content of from 20 to 80% byweight, a melt flow rate (MFR) of from 25 to 140 g/10 min and anethylene triad sequence fraction of from 55 to 70%, and talc.

JP 2000-26697 A discloses a propylene-based resin composition whichincludes a propylene-ethylene block copolymer including a crystallinepolypropylene hompolymer portion and an ethylene-propylene randomcopolymer portion having an ethylene content of 30% by weight or moreand a weight average molecular weight of from 200,000 to 1,000,000; anethylene-α-olefin or ethylene-α-olefin-diene copolymer rubber having anMFR of from 0.05 to 1.2 g/10min; talc and a high density polyethylenehaving an MFR of 11 g/10 min or more.

JP 2000-178389 A discloses a polypropylene resin composition whichincludes a propylene-ethylene block copolymer including a propylenehomopolymer portion wherein the MFR of the propylene homopolymer portionis 100 g/10 min or more and the MFR of the block copolymer is from 55 to200 g/10 min; an ethylene-α-olefin copolymer rubber having an MFR ofless than 0.9 g/10 min and a comonomer content of 28% by weight or more;and talc.

However, regarding molded articles made from the polypropylene resincompositions disclosed in the above-cited references, there are demandsfor improvement in balance between rigidity and impact resistance andelimination of weld lines.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a polypropylene resincomposition which has superior fluidity and which is useful as a rawmaterial of molded articles having good balance between rigidity andimpact resistance and having, if any, an unnoticeable weld line, and toprovide a molded article made therefrom.

The present invention provides, in one aspect,

a polypropylene resin composition comprising:

from 50 to 93% by weight of a polypropylene resin (A),

from 1 to 25% by weight of an ethylene-α-olefin copolymer rubber (B)which includes units of an α-olefin having from 4 to 12 carbon atoms andethylene units and has a density of from 0.850 to 0.870 g/cm³ and a meltflow rate, as measured at a temperature of 230° C. and a load of 2.16kgf, of from 0.05 to 1 g/10 min,

from 1 to 25% by weight of an ethylene-α-olefin copolymer rubber (C)which includes units of an α-olefin having from 4 to 12 carbon atoms andethylene units and has a density of from 0.850 to 0.870 g/cm³ and a meltflow rate, as measured at a temperature of 230° C. and a load of 2.16kgf, of from 2 to 20 g/10 min, and

from 5 to 25% by weight of an inorganic filler (D), provided that theoverall amount of the polypropylene resin composition is 100% by weight,wherein the polypropylene resin (A) is a propylene-ethylene blockcopolymer (A-1) satisfying requirements (1), (2), (3) and (4) definedbelow or a polymer mixture (A-3) comprising the block copolymer (A-1)and a propylene homopolymer (A-2),

requirement (1): the block copolymer (A-1) is a propylene-ethylene blockcopolymer comprising from 55 to 90% by weight of a polypropylene portionand from 10 to 45% by weight of a propylene-ethylene random copolymerportion, provided that the overall amount of the block copolymer (A-1)is 100% by weight,

requirement (2): the polypropylene portion of the block copolymer (A-1)is a propylene homopolymer or a copolymer comprising propylene units and1 mol % or less of units of a comonomer selected from the groupconsisting of ethylene and α-olefin having 4 or more carbon atoms,provided that the overall amount of units constituting the copolymer is100 mol %,

requirement (3): the weight ratio of the propylene units to the ethyleneunits in the propylene-ethylene random copolymer portion of the blockcopolymer (A-1) is from 65/35 to 52/48,

requirement (4): the propylene-ethylene random copolymer portion of theblock copolymer (A-1) has an intrinsic viscosity [η]_(EP-A) of not lessthan 2.2 dl/g but less than 4 dl/g.

In a preferred embodiment,

-   the ratio of the content in weight of the ethylene-α-olefin    copolymer rubber (B) to the content in weight of the    ethylene-α-olefin copolymer rubber (C) is from 15/85 to 85/15; or,-   the polypropylene portion of the block copolymer (A-1) has an    intrinsic viscosity [η]_(P) of from 0.7 dl/g to 1.3 dl/g and a    molecular weight distribution, as measured by GPC, of not less than    3 but less than 7; or,-   the polypropylene portion of the block copolymer (A-1) has an    isotactic pentad fraction of 0.97 or more; or,-   the inorganic filler (D) is talc.

In another aspect, the present invention provides an injection moldedarticle made from the polypropylene resin composition mentioned above.

According to the present invention, it is possible to obtain apolypropylene resin composition which has superior fluidity and which isuseful as a raw material of molded articles having good balance betweenrigidity and impact resistance and having, if any, an unnoticeable weldline, and to obtain a molded article made therefrom which has goodbalance between rigidity and impact resistance and has, if any, anunnoticeable weld line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view showing a flat molded article for use inevaluation of appearance. In the figure, 1: gate 2: gate, 3: weld line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polypropylene resin composition of the present invention is apolypropylene resin composition including from 50 to 93% by weight of apolypropylene resin (A), from 1 to 25% by weight of an ethylene-α-olefincopolymer rubber (B), from 1 to 25% by weight of an ethylene-α-olefincopolymer rubber (C), and from 5 to 25% by weight of an inorganic filler(D), provided that the overall amount of the polypropylene resincomposition is 100% by weight.

The polypropylene resin (A) is a propylene-ethylene block copolymer(A-1) or a polymer mixture (A-3) including the block copolymer (A-1) anda propylene homopolymer (A-2).

The propylene-ethylene block copolymer (A-1) is a propylene-ethyleneblock copolymer including from 55 to 90% by weight of a polypropyleneportion and from 10 to 45% by weight of a propylene-ethylene randomcopolymer portion, provided that the overall amount of the blockcopolymer is 100% by weight.

The block copolymer (A-1) preferably includes from 65 to 88% by weightof a polypropylene portion and from 12 to 35% by weight of apropylene-ethylene random copolymer portion, and more preferablyincludes from 70 to 85% by weight of a polypropylene portion and from 15to 30% by weight of a propylene-ethylene random copolymer portion.

When the amount of the polypropylene portion is less than 55% by weight,the rigidity or hardness of molded articles made from the polypropyleneresin composition may fail or the polypropylene resin composition mayhave an insufficient moldability because of failure in fluidity, whereaswhen the amount of the polypropylene portion is over 90% by weight, thetoughness or impact resistance of molded articles may fail.

The polypropylene portion of the block copolymer (A-1) is a propylenehomopolymer or a copolymer comprising propylene units and 1 mol % orless of units of a comonomer selected from the group consisting ofethylene and α-olefin having 4 or more carbon atoms, provided that theoverall amount of units constituting the copolymer is 100 mol %. Theabove-mentioned α-olefins having 4 or more carbon atoms are preferablyα-olefins having from 4 to 8 carbon atoms, examples of which include1-butene, 1-hexene and 1-octene.

In the case where the polypropylene portion of the block copolymer (A-1)is a copolymer including propylene units and units of a comonomerselected from the group consisting of ethylene and α-olefins having 4 ormore carbon atoms, when the content of the comonomer units is more than1 mol %, the rigidity, heat resistance or hardness of molded articlesmade from the polypropylene resin composition may fail.

From the viewpoint of rigidity, heat resistance or hardness of moldedarticles made from a polypropylene resin composition, the polypropyleneportion in the block copolymer (A-1) is preferably a propylenehomopolymer, more preferably a propylene homopolymer having an isotacticpentad fraction, as measured by ¹³C-NMR, of 0.97 or more. More preferredis a propylene homopolymer having an isotactic pentad fraction of 0.98or more.

The isotactic pentad fraction is a fraction of propylene monomer unitsexisting at the center of an isotactic chain in the form of a pentadunit, in other words, the center of a chain in which five propylenemonomer units are meso-bonded successively, in the polypropylenemolecular chain as measured by a method reported in A. Zambelli et al.,Macromolecules, 6, 925 (1973), namely, by use of ¹³C-NMR. The assignmentof NMR absorption peaks is carried out according to the disclosure ofMacromolecules, 8, 687 (1975).

Specifically, the isotactic pentad fraction is measured as an areafraction of mmmm peaks in all the absorption peaks in the methyl carbonregion of a ¹³C-NMR spectrum. According to this method, the isotacticpentad fraction of an NPL standard substance, CRM No. M19-14Polypropylene PP/MWD/2 available from NATIONAL PHYSICAL LABORATORY, G.B.was measured to be 0.944.

From the viewpoint of balance between fluidity of a resin composition inits molten state and toughness of molded articles, the intrinsicviscosity [η]_(P) of the polypropylene portion of the block copolymer(A-1) is preferably from 0.7 to 1.3 dl/g, and more preferably from 0.85to 1.1 dl/g. The intrinsic viscosity is measured in Tetralin at 135° C.

The molecular weight distribution, as measured by gel permeationchromatography (GPC), of the polypropylene portion of the blockcopolymer (A-1) is preferably not less than 3 but less than 7, morepreferably from 3 to 5. As well known in the art, the molecular weightdistribution, which is also referred to as a Q factor, is a ratio of theweight average molecular weight to the number average molecular weight,both average molecular weight being determined by GPC measurement.

From the viewpoint of balance between rigidity and impact resistance ofmolded articles made from a resin composition, the weight ratio of thepropylene units to the ethylene units in the propylene-ethylene randomcopolymer portion of the block copolymer (A-1) is from 65/35 to 52/48,preferably from 62/38 to 55/45.

From the viewpoints of prevention of occurrence of weld lines at thetime of molding of a resin composition and balance between rigidity andimpact resistance of resulting molded articles, the intrinsic viscosity[η]_(EP-A) of the propylene-ethylene random copolymer portion of theblock copolymer (A-1) is not less than 2.2 dl/g but less than 4 dl/g,and preferably from 2.5 to 3.5.

From the viewpoints of moldability of a resin composition and the impactresistance of molded articles, the melt flow rate (MFR), as measured ata temperature of 230° C. and a load of 2.16 kgf, of thepropylene-ethylene block copolymer (A-1) is preferably from 10 to 120g/10 min, and more preferably from 20 to 53 g/10 min.

The propylene-ethylene block copolymer (A-1) can be produced, forexample, by a conventional polymerization method using a catalyst systemobtained by causing (a) a solid catalyst component including magnesium,titanium, halogen and an electron donor as essential components tocontact with (b) an organoaluminum compound and (c) an electron donorcomponent. This type of catalyst can be prepared by the methodsdisclosed in JP 1-319508 A, JP 7-216017 A and JP 10-212319 A.

The propylene-ethylene block copolymer (A-1) can be produced, forexample, by a method including at least two stages wherein apolypropylene portion is produced in a first step and then apropylene-ethylene random copolymer having an ethylene unit content offrom 35 to 48% by weight is produced in a second step.

Examples of the method of polymerization include bulk polymerization,solution polymerization, slurry polymerization and vapor phasepolymerization. These polymerization techniques may be conducted eitherbatchwise or continuously. Moreover, these may be optionally combined.From industrial and economic points of view, continuous vapor phasepolymerization and continuous bulk-vapor phase polymerization arepreferred.

More specific preferable examples are:

(1) a method in which in a polymerization apparatus including two ormore polymerization reactors arranged in series, in the presence of theaforesaid catalyst system obtained by causing (a) a solid catalystcomponent to contact with (b) an organoaluminum compound and (c) anelectron donor component, a polypropylene portion is produced in a firstpolymerization reactor and the product is transferred to a secondpolymerization reactor and then a propylene-ethylene random copolymerportion having an ethylene unit content of from 35 to 48% by weight andan intrinsic viscosity of not less than 2.2 dl/g but less than 4 dl/g isproduced continuously in the second polymerization reactor, and

(2) a method in which in a polymerization apparatus including four ormore polymerization reactors arranged in series, in the presence of theaforesaid catalyst system obtained by causing (a) a solid catalystcomponent to contact with (b) an organoaluminum compound and (c) anelectron donor component, a polypropylene portion is produced in a firstand second polymerization reactors and the product is transferred to athird polymerization reactor and then a propylene-ethylene randomcopolymer portion having an ethylene unit content of from 35 to 48% byweight and an intrinsic viscosity of not less than 2.2 dl/g but lessthan 4 dl/g is produced continuously in the third and fourthpolymerization reactors.

The amounts of the solid catalyst component (a), the organoaluminumcompound (b) and the electron-donating component (c) and the manners inwhich each catalyst component is fed into the polymerization reactorsmay be determined appropriately according to conventional ways for useof conventional catalysts.

The polymerization temperature usually ranges from −30 to 300° C. andpreferably from 20 to 180° C. The polymerization pressure is usuallyfrom an ambient pressure to 10 MPa and preferably from 0.2 to 5 MPa. Amolecular weight regulator, e.g. hydrogen, may be used.

In the production of the propylene polymer (A-1), pre-polymerization maybe carried out before the main polymerization. An available method ofpreliminary polymerization is polymerization carried out by feeding asmall amount of propylene in the presence of a solid catalyst component(a) and an organoaluminum compound (b) in a slurry state using asolvent.

Additives may optionally be added to the block copolymer (A-1). Examplesof the additives include antioxidants, UV absorbers, lubricants,pigments, antistatic agents, copper inhibitors, flame retardants,neutralizing agents, foaming agents, plasticizers, nucleating agents,foam inhibitors and crosslinking agents. For improvement in heatresistance, weatherability and stability against oxidization, it ispreferable to add an antioxidant or a UV absorber.

The block copolymer (A-1) may be not only a polymer produced by theaforementioned method, but also a polymer obtained by subjecting thepolymer produced by the aforementioned method to decomposition treatmentincluding addition of a peroxide followed by melt-kneading.

The intrinsic viscosity [η]_(EP-A) of the propylene-ethylene randomcopolymer portion included in the polymer obtained by the decompositiontreatment is determined through measurement of an intrinsic viscosity ofthe polymer's component soluble in 20° C. xylene.

As the peroxide, an organic peroxide is typically used, examples ofwhich include alkyl peroxides, diacyl peroxides, peroxyesters andperoxycarbonates.

Examples of the alkyl peroxides include dicumylperoxide, di-tert-butylperoxide, tert-butylcumyl peroxide,2,5-dimethyl-2,5-di(tert-butylperoxyl)hexane,2,5-dimethyl-2,5-di(tert-butylperoxyl)hexyne-3, tert-butyl cumylperoxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, and3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxononane.

Examples of the diacyl peroxides include benzoyl peroxide, lauroylperoxide and decanoyl peroxide.

Examples of the peroxyesters include 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumyl peroxyneodecanoate, tert-butylperoxyneodecanoate, tert-butyl peroxyneoheptanoate, tert-butylperoxypivalate, tert-hexyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, di-tert-butylperoxyhexahydroterephthalate, tert-amylperoxyl-3,5,5-trimethylhexanoate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butylperoxybenzoate, and di-tert-butyl peroxytrimethyladipate.

Examples of the peroxycarbonates include di-3-methoxybutylperoxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, diisopropylperoxydicarbonate, tert-butyl peroxyisopropylcarbonate,di(4-tert-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate,and dimyristyl peroxydicarbonate.

The polypropylene resin (A) included in the polypropylene resincomposition of the present invention may be the aforesaid blockcopolymer (A-1) or a polymer mixture (A-3) including the aforesaid blockcopolymer (A-1) and a propylene homopolymer (A-2).

In typical cases, the content of the block copolymer (A-1) included inthe polymer mixture (A-3) is from 30 to 99% by weight and the content ofthe propylene homopolymer (A-2) is from 1 to 70% by weight. The contentof the block copolymer (A-1) is preferably from 45 to 90% by weight andthe content of the propylene homopolymer (A-2) is preferably from 10 to55% by weight.

The homopolymer (A-2) is preferably a homopolymer having an isotacticpentad fraction of 0.97 or more, more preferably a homopolymer having anisotactic pentad fraction of 0.98 or more.

The melt flow rate, as measured at a temperature of 230° C. and a loadof 2.16 kgf, of the homopolymer (A-2) is typically from 10 to 500 g/10min, preferably from 40 to 350 g/10 min.

The homopolymer (A-2) can be produced by polymerization using a catalystsimilar to that for use in the preparation of the block copolymer (A-1).

The content of the polypropylene resin (A) included in the polypropyleneresin composition of the present invention is from 50 to 93% by weight,preferably from 55 to 90% by weight, and more preferably from 60 to 85%by weight, provided that the overall amount of the polypropylene resincomposition is 100% by weight.

When the content of the polypropylene resin (A) is less than 50% byweight, the rigidity of molded articles made from the polypropyleneresin composition may fail, whereas when the content is over 93% byweight, the impact strength of such molded articles may fail.

The ethylene-α-olefin copolymer rubber (B) is an ethylene-α-olefincopolymer rubber including units of an α-olefin having 4-12 carbon atomsand ethylene units, the rubber having a density of from 0.850 to 0.870g/cm³ and a melt flow rate, as measured at a temperature of 230° C. anda load of 2.16 kgf, of from 0.05 to 1 g/10 min.

Examples of the α-olefin having 4-12 carbon atoms include butene-1,pentene-1, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1and octene-1 are preferred.

From the viewpoint of impact strength, particularly low-temperatureimpact strength, of molded articles, the content of α-olefin unitsincluded in the copolymer rubber (B) is typically from 20 to 50% byweight, and preferably from 24 to 50% by weight, provided that theoverall amount of the copolymer rubber (B) is 100% by weight.

Examples of the copolymer rubber (B) include ethylene-butene-1 randomcopolymer rubber, ethylene-hexene-1 random copolymer rubber andethylene-octene-1 random copolymer rubber. Ethylene-octene-1 randomcopolymer or ethylene-butene-1 random copolymer is preferred. Two ormore ethylene-α-olefin copolymer rubbers may be used together.

From the viewpoint of balance between rigidity and impact resistance ofmolded articles made from the resin composition, the density of thecopolymer rubber (B) is typically from 0.850 to 0.870 g/cm³, andpreferably from 0.850 to 0.865 g/cm³.

From the viewpoints of prevention of occurrence of weld lines at thetime of molding of a resin composition and balance between rigidity andimpact resistance of resulting molded articles, the melt flow rate, asmeasured at a temperature of 230° C. and a load of 2.16 kgf, of thecopolymer rubber (B) is typically from 0.05 to 1 g/10 min, andpreferably from 0.2 to 1 g/10 min.

The copolymer rubber (B) can be prepared by copolymerizing ethylene andα-olefin using a conventional catalyst and a conventional polymerizationmethod.

Examples of the conventional catalyst include a catalyst system composedof a vanadium compound and an organoaluminum compound, a Ziegler-Nattacatalyst system or a metallocene catalyst system. The conventionalpolymerization method may be solution polymerization, slurrypolymerization, high pressure ion polymerization or vapor phasepolymerization.

The content of the copolymer rubber (B) included in the polypropyleneresin composition of the present invention is from 1 to 25% by weight,preferably from 3 to 22% by weight, and more preferably from 5 to 20% byweight, provided that the overall amount of the polypropylene resincomposition is 100% by weight.

When the content of the copolymer rubber (B) is less than 1% by weight,the impact strength of molded articles made from the polypropylene resincomposition may fail, whereas when the content is over 25% by weight,the rigidity of molded articles may fail.

The ethylene-α-olefin copolymer rubber (C) as used herein is anethylene-α-olefin copolymer rubber which includes α-olefin units having4-12 carbon atoms and ethylene units and which has a density of from0.850 to 0.870 g/cm³ and a melt flow rate, as measured at a temperatureof 230° C. and a load of 2.16 kgf, of from 2 to 20 g/10 min.

Examples of the α-olefin having 4-12 carbon atoms include butene-1,pentene-1, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1and octene-1 are preferred.

From the viewpoint of impact strength, particularly low-temperatureimpact strength, of molded articles made from the resin composition, thecontent of α-olefin units included in the copolymer rubber (C) istypically from 20 to 50% by weight, and preferably from 24 to 50% byweight, provided that the overall amount of the copolymer rubber (C) is100% by weight.

Examples of the copolymer rubber (C) include ethylene-butene-1 randomcopolymer rubber, ethylene-hexene-1 random copolymer rubber andethylene-octene-1 random copolymer rubber. Ethylene-octene-1 randomcopolymer or ethylene-butene-1 random copolymer is preferred. Two ormore ethylene-α-olefin random copolymer rubbers may be used incombination.

From the viewpoint of balance between rigidity and impact resistance ofmolded articles made from the resin composition, the density of thecopolymer rubber (C) is typically from 0.850 to 0.870 g/cm³, andpreferably from 0.850 to 0.865 g/cm³.

From the viewpoint of balance between rigidity and impact resistance ofmolded articles made from the resin composition, the melt flow rate, asmeasured at a temperature of 230° C. and a load of 2.16 kgf, of thecopolymer rubber (C) is from 2 to 20 g/10 min, preferably from 2.3 to 15g/10 in, and more preferably from 2.5 to 10 g/10 min.

The copolymer rubber (C) can be produced by a method the same as thatused for the production of the copolymer rubber (B).

The content of the copolymer rubber (C) included in the polypropyleneresin composition of the present invention is from 1 to 25% by weight,preferably from 3 to 22% by weight, and more preferably from 5 to 20% byweight, provided that the overall amount of the polypropylene resincomposition is 100% by weight.

When the content of the copolymer rubber (C) is less than 1% by weight,the impact strength of molded articles made from the polypropylene resincomposition may fail, whereas when the content is over 25% by weight,the rigidity of molded articles may fail.

From the viewpoints of prevention of occurrence of weld lines at thetime of molding of a resin composition and balance between rigidity andimpact resistance of resulting molded articles, the ratio of the contentin weight of the copolymer rubber (B) to the content in weight of thecopolymer rubber (C) is preferably from 15/85 to 85/15, and morepreferably from 35/65 to 75/25.

Examples of the inorganic filler (D) include calcium carbonate, bariumsulfate, mica, crystalline calcium silicate, talc and fibrous magnesiumoxysulfate. Talc or fibrous magnesium oxysulfate is preferred. Two ormore sorts of inorganic filler may be used together.

The talc to be used as inorganic filler (D) is preferably one preparedby grinding hydrous magnesium silicate. The crystal structure of themolecule of the hydrous magnesium silicate is a pyrophyllite typethree-layer structure. Talc comprises a lamination of this structure andpreferably is a tabular powder obtained by fine pulverization of itscrystals almost into its unit layers.

The talc preferably has an average particle diameter of 3 μm or less. Bythe average particle diameter of talc is meant a 50% equivalent particlediameter D50 calculated from an integrated distribution curve by theminus sieve method measured by suspending talc in a dispersion medium(water or alcohol) using a centrifugal sedimentation particle sizedistribution measuring device.

The inorganic filler (D) may be used without being subjected to anytreatment or may be used after being surface treated with various typesof surfactant for improving interfacial adhesiveness with ordispersibility in the polypropylene resin (A). The surfactant isexemplified by silane coupling agents, titanium coupling agents, higherfatty acids, higher fatty acid esters, higher fatty acid amides andhigher fatty acid salts.

The average fiber length of fibrous magnesium oxysulfate to be used asthe inorganic filler (D) is preferably from 5 to 50 μm, more preferablyfrom 10 to 30 μm. The fibrous magnesium oxysulfate preferably has anaverage fiber diameter of from 0.3 to 2 μm, more preferably from 0.5 to1 μm.

The content of the inorganic filler (D) included in the polypropyleneresin composition of the present invention is from 5 to 25% by weight,preferably from 7 to 23% by weight, and more preferably from 10 to 22%by weight, provided that the overall amount of the polypropylene resincomposition is 100% by weight.

When the content of the inorganic filler (D) is less than 5% by weight,the rigidity of molded articles made from the polypropylene resincomposition may fail, whereas when the content is over 25% by weight,the impact strength of molded articles may fail.

The polypropylene resin composition of the present invention can beproduced by melt-kneading its components. For the kneading, a kneadingdevice such as a single screw extruder, a twin screw extruder, a Banburymixer and heated rolls may be used. The kneading temperature istypically from 170 to 250° C., and the kneading time is typically from 1to 20 minutes. All the components may be kneaded at the same time orsuccessively.

The method for kneading the components successively may be any ofoptions (1), (2) and (3) shown below.

(1) A method which includes kneading and pelletizing the aforesaid blockcopolymer (A-1) first and then kneading the pellets, the aforesaidcopolymer rubber (B), the aforesaid copolymer rubber (C) and theaforesaid inorganic filler (D) together.

(2) A method which includes kneading and pelletizing the aforesaid blockcopolymer (A-1) first and then kneading the pellets, the aforesaidhomopolymer (A-2), the aforesaid copolymer rubber (B), the aforesaidcopolymer rubber (C), and the aforesaid inorganic filler (D) together.

(3) A method which includes kneading the aforesaid block copolymer(A-1), the aforesaid copolymer rubber (B) and the aforesaid copolymerrubber (C) and then adding the aforesaid inorganic filler (D), followedby kneading.

(4) A method which includes kneading the aforesaid block copolymer (A-1)and the aforesaid inorganic filler (D) and then adding the aforesaidcopolymer rubber (B) and the aforesaid copolymer rubber (C), followed bykneading.

In the method (3) or (4), a propylene homopolymer (A-2) may optionallybe added.

The polypropylene resin composition of the present invention may includea variety of additives. Examples of the additives include antioxidants,UV absorbers, lubricants, pigments, antistatic agents, copperinhibitors, flame retardants, neutralizing agents, foaming agents,plasticizers, nucleating agents, foam inhibitors and crosslinkingagents. In order to improve heat resistance, weather resistance andstability against oxidation, addition of an antistatic agent or a UVabsorber is preferred. The content of each additive is typically from0.001 to 1% by weight.

The polypropylene resin composition of the present invention may includean aromatic vinyl compound-containing rubber to improve the balance ofmechanical properties.

Examples of the aromatic vinyl compound-containing rubber include blockcopolymers composed of aromatic vinyl compound polymer blocks andconjugated diene polymer blocks. Moreover, hydrogenated block copolymersderived from block copolymers composed of aromatic vinyl compoundpolymer blocks and conjugated diene polymer blocks through hydrogenationat all or part of their double bonds in their conjugated diene blocksare also available. The degree of hydrogenation of the double bonds ofthe conjugated diene polymer blocks is preferably 80% by weight or more,more preferably 85% by weight or more, provided that the overall amountof the double bonds in the conjugated diene polymer blocks is 100% byweight.

The molecular weight distribution, as determined by gel permeationchromatography (GPC), of the aromatic vinyl compound-containing rubberis preferably 2.5 or less, more preferably from 1 to 2.3.

The content of units derived from aromatic vinyl compounds is preferablyfrom 10 to 20% by weight, more preferably from 12 to 19% by weight,provided that the overall amount of the aromatic vinylcompound-containing rubber is 100% by weight.

The melt flow rate, as measured at a temperature of 230° C. and a loadof 2.16 kgf according to JIS K6758, of the aromatic vinylcompound-containing rubber is preferably from 0.01 to 15 g/10 min, andmore preferably from 0.03 to 13 g/10 min.

Specific examples of the aromatic vinyl compound-containing rubberinclude block copolymers such as styrene-ethylene-butene-styrene rubber(SEBS), styrene-ethylene-propylene-styrene rubber (SEPS),styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS)and styrene-isoprene-styrene rubber (SIS), and block copolymersresulting from hydrogenation of the foregoing block copolymers.Furthermore, rubbers obtained by causing an aromatic vinyl compound suchas styrene to react with an ethylene-propylene-nonconjugated dienerubber (EPDM) may also be used. Two or more aromatic vinylcompound-containing rubbers may be used in combination.

The aromatic vinyl compound-containing rubber may be produced by amethod in which an aromatic vinyl compound is bonded to an olefin-basedcopolymer rubber or a conjugated diene rubber through polymerization ora reaction.

The injection molded article of the present invention is one obtained bya known injection molding of the polypropylene resin composition of thepresent invention.

Reflecting the characteristics of the polypropylene resin compositionused as a raw material thereof, such injection molded articles have, ifany, an unnoticeable weld line and are superior in balance betweenrigidity and impact strength.

The injection molded article of the present invention can be suitablyused particularly as automotive components such as door trims, pillars,instrument panels and bumpers.

EXAMPLES

The present invention will be explained below with reference to examplesand comparative example. Methods for measuring physical properties ofpolymers and compositions of the present invention and those of theExamples and Comparative Examples are described below.

(1) Intrinsic Viscosity (Unit: dl/g)

Reduced viscosities were measured at three concentrations of 0.1, 0.2and 0.5 g/dl using a Ubbelohde viscometer. The intrinsic viscosity wascalculated by a calculation method described in “Kobunshi Yoeki (PolymerSolution), Kobunshi Jikkengaku (Polymer Experiment Study) 11” page 491(published by Kyoritsu Shuppan Co., Ltd., 1982), namely, by anextrapolation method in which reduced viscosities are plotted againstconcentrations and the concentration is extrapolated in zero. Themeasurements were carried out at 135° C. using Tetralin as a solvent.

(1-1) Intrinsic Viscosity of Propylene-Ethylene Block Copolymer

(1-1a) Intrinsic Viscosity of Polypropylene Portion: [η]_(P)

The intrinsic viscosity [η]_(P) of the polypropylene portion included ina propylene-ethylene block copolymer was determined by the methoddescribed in (1) above using some polymer powder sampled from apolymerization reactor just after the first step for producing thepolypropylene portion during the production of the propylene-ethyleneblock copolymer.

(1-1b) Intrinsic Viscosity of Propylene-Ethylene Random CopolymerPortion: [η]_(EP)

The intrinsic viscosity [η]_(P) of the propylene homopolymer portionincluded in a propylene-ethylene block copolymer and the intrinsicviscosity [η]_(T) of the propylene-ethylene block copolymer weremeasured by the method described in (1) above. Then, the intrinsicviscosity [η]_(EP) of the propylene-ethylene random copolymer portion inthe propylene-ethylene block copolymer was determined from the equationprovided below by use of a weight ratio, X, of the propylene-ethylenerandom copolymer to the propylene-ethylene block copolymer. The weightratio X was determined by the method of (2) provided below.[η]_(EP)=[η]_(T) /X−(1/X−1)[η]_(P)

[η]_(P): Intrinsic viscosity (dl/g) of propylene homopolymer portion

[η]_(T): Intrinsic viscosity (dl/g) of propylene-ethylene blockcopolymer

The intrinsic viscosity [μ]_(EP) of a propylene-ethylene randomcopolymer portion included in a propylene-ethylene block copolymerthermally decomposed with peroxide was an intrinsic viscosity of acomponent soluble in 20° C. xylene obtained by the method shown below.

[Component Soluble in 20° C. Xylene]

A propylene-ethylene block copolymer 5 g was dissolved completely in 500ml of boiling xylene, then cooled to 20° C. and left to stand for fourhours. The mixture was then filtered so that the matter insoluble in 20°C. was removed. The filtrate was concentrated through evaporation ofxylene, followed by drying at 60° C. under reduced pressure. Thus, apolymer component soluble in 20° C. xylene was obtained.

(2) Weight Ratio of the Propylene-Ethylene Random Copolymer Portion tothe Propylene-Ethylene Block Copolymer: X and Ethylene Content of thePropylene-Ethylene Random Copolymer Portion in the Propylene-EthyleneBlock Copolymer: [(C2′)_(EP)]

The above values were calculated from a ¹³C-NMR spectrum measured asdescribed below according to the report of Kakugo, et al.(Macromolecules, 15, 1150-1152 (1982)).

In a test tube having a diameter of 10 mm, about 200 mg of apropylene-ethylene block copolymer was uniformly dissolved in 3 ml ofo-dichlorobenzene to yield a sample solution, which was measured for its¹³C-NMR spectrum under the following conditions:

Temperature: 135° C.

Pulse repeating time: 10 seconds

Pulse width: 45°

Accumulation number: 2500 times

(3) Melt Flow Rate (MFR, Unit: g/10 min)

The melt flow rate was measured according to the method provided in JISK6758. The measurement was carried out at a temperature of 230° C. and aload of 2.16 kgf, unless otherwise stated.

(4) Tensile Testing (Breaking Elongation (UE), Unit: %))

The breaking elongation was measured according to the method provided inASTM D638. The breaking elongation (UE) was evaluated at a tensile rateof 20 mm/min by use of a 3.2 mm thick specimen produced by injectionmolding.

(5) Flexural Modulus (FM, Unit: MPa)

The flexural modulus was measured according to the method provided inJIS K 7203. The measurement was carried out at a load rate of 2.0 mm/minand a temperature of 23° C. using an injection molded specimen having athickness of 6.4 mm and a span length of 100 mm.

(6) Izod Impact Strength (Izod, Unit: kJ/m²)

The Izod impact strength was measured according to the method providedin JIS K7110. The measurement was carried out at a temperature of 23° C.or −30° C. using a 6.4 mm thick notched specimen which was produced byinjection molding followed by notching.

(7) Heat Distortion Temperature (HDT, Unit: ° C.)

The heat distortion temperature was measured according to the methodprovided in JIS K7207 at a fiber stress of 1.82 kgf/cm².

(8) Rockwell Hardness (HR, in R Scale)

The Rockwell hardness was measured according to the method provided inJIS K7202. The measurement was carried out using a 3.0 mm thick specimenprepared by injection molding. The measurements are shown in R scale.

(9) Brittle Point (BP, Unit: ° C.)

The brittle point was measured according to the method provided in JIS K7216. The measurement was carried out using a specimen with dimensions6.3×38×2 mm punched out from an injection molded plate with dimensions25×150×2 mm.

(10) Isotactic Pentad Fraction ([mmmm])

The isotactic pentad fraction is a fraction of propylene monomer unitsexisting at the center of an isotactic chain in the form of a pentadunit, in other words, the center of a chain in which five propylenemonomer units are meso-bonded successively, in the polypropylenemolecular chain as measured by a method disclosed in A. Zambelli et al.,Macromolecules, 6, 925 (1973), namely, by use of ¹³C-NMR. The assignmentof NMR absorption peaks was conducted according to Macromolecules, 8,687 (1975).

Specifically, the isotactic pentad fraction was measured as an areafraction of mmmm peaks in all the absorption peaks in the methyl carbonregion of a ¹³C-NMR spectrum. According to this method, the isotacticpentad fraction of an NPL standard substance, CRM No. M19-14Polypropylene PP/MWD/2 available from NATIONAL PHYSICAL LABORATORY, G.B.was measured to be 0.944.

(11) Molecular Weight Distribution

The molecular weight distribution was measured by gel permeationchromatography (GPC) under the following conditions:

Instrument: Model 150CV (manufactured by Millipore Waters Co.)

Column: Shodex M/S 80

Measurement temperature: 145° C.

Solvent: o-Dichlorobenzene

Sample concentration: 5 mg/8 mL

A calibration curve was produced using a standard polystyrene. The Mw/Mnof a standard polystyrene (NBS706; Mw/Mn=2.0) measured under the aboveconditions was 1.9-2.0.

[Production of Injection Molded Article: #1]

Specimens (injection-molded articles) for evaluation of physicalproperties in the above-mentioned (4)-(7) were prepared by injectionmolding at a molding temperature of 220° C., a mold cooling temperatureof 50° C., an injection time of 15 seconds and a cooling time of 30seconds using an injection molding machine, model IS150E-V, manufacturedby Toshiba Machine Co., Ltd.

(12) Preparation of Injection Molded Article for Evaluation ofOccurrence of Weld Line

An injection molded article, which is a specimen for use in evaluationof occurrence of weld lines, was prepared by the following method.

Molding was carried out at a molding temperature of 220° C. by use of aninjection molding machine SE180D (manufactured by Sumitomo HeavyIndustries, Ltd.) having a clamping force of 180 tons, equipped with amold with cavity dimensions of 100×400×3.0 mm having twin parallelgates. Thus, a flat molded article shown in FIG. 1 was produced. In FIG.1, numerals 1 and 2 each represent gates and 3 represents a weld line.

(13) Occurrence of Weld Line

Using the flat molded article prepared by the method of (12) above, aweld line was visually observed. The length and noticeability of a weldline shown in FIG. 1 were observed. The shorter the weld line, thebetter the appearance.

(14) Density

The density of a polymer was measured according to the method providedin JIS K7112.

The methods for preparing four types of catalyst (solid catalystcomponents (I), (II), (III) and (IV)) used in the preparations of thepolymers used in Examples and Comparative Examples are shown below.

(1) Solid Catalyst Component (I)

(1-1) Preparation of Reduced Solid Product

A 500-ml flask equipped with a stirrer and a dropping funnel was purgedwith nitrogen, and then 290 ml of hexane, 8.9 ml (8.9 g, 26.1 mmol) oftetrabutoxytitanium, 3.1 ml (3.3 g, 11.8 mmol) of diisobutyl phthalateand 87.4 ml (81.6 g, 392 mmol) of tetraethoxysilane were fed therein toyield a homogeneous solution. Subsequently, 199 ml of a solution ofn-butylmagnesium chloride in di-n-butyl ether (manufactured by YukiGosei Kogyo Co., Ltd., n-butylmagnesium chloride concentration: 2.1mmol/ml) was slowly added dropwise from the dropping funnel thereto over5 hours while the temperature in the flask was maintained at 6° C. Aftercompletion of the dropping, the mixture was stirred at 6° C. for 1 hour,and additionally stirred for 1 hour at room temperature. Thereafter, themixture was subjected to solid-liquid separation. The resulting solidwas washed repeatedly with three portions of 260-ml toluene and then aproper amount of toluene was added thereto to adjust the slurryconcentration to 0.176 g/ml. After sampling a part of the solid productslurry, its composition analysis was conducted, and as a result, thesolid product was found to include 1.96% by weight of titanium atoms,0.12% by weight of phthalic acid ester, 37.2% by weight of ethoxy groupsand 2.8% by weight of butoxy groups.

(1-2) Preparation of Solid Catalyst Component

A 100 ml flask equipped with a stirrer, a dropping funnel and athermometer was purged with nitrogen. Then, 52 ml of the slurryincluding the solid product obtained in the above (1) was fed in theflask, and 25.5 ml of supernatant was removed. Following addition of amixture of 0.80 ml (6.45 mmol) of di-n-butyl ether and 16.0 ml (0.146mol) of titanium tetrachloride and subsequent addition of 1.6 ml (11.1mmol: 0.20 ml/1 g-solid product), the system was heated to 115° C. andstirred for 3 hours. After completion of the reaction, the reactionmixture was subjected to solid-liquid separation at that temperature,followed by washing with two portions of 40-ml toluene at the sametemperature. Subsequently, 10.0 ml of toluene and a mixture of 0.45 ml(1.68 mmol) of diisobutyl phthalate, 0.80 ml (6.45 mmol) of di-n-butylether and 8.0 ml (0.073 mol) of titanium tetrachloride were added to thesolid, followed by a treatment at 115° C. for 1 hour. After completionof the reaction, the reaction mixture was subjected to solid-liquidseparation at that temperature. The resulting solid was then washed withthree portions of 40-ml toluene at that temperature and additionallywith three portions of 40-ml hexane, and then dried under reducedpressure to yield 7.36 g of a solid catalyst component. The solidcatalyst component was found to include 2.18% by weight of titaniumatoms, 11.37% by weight of phthalic acid ester, 0.3% by weight of ethoxygroups and 0.1% by weight of butoxy groups. An observation of the solidcatalyst component by a stereomicroscope revealed that the componentincluded no fine powder and had a good powder property. This solidcatalyst component is hereinafter called solid catalyst component (I).

(2) Solid Catalyst Component (II)

A 200-L SUS reactor equipped with a stirrer was purged with nitrogen,and then 80 L of hexane, 6.55 mol of tetrabutoxytitanium and 98. 9 molof tetraethoxysilane were fed to form a homogeneous solution.Subsequently, 50 L of a solution of butylmagnesium chloride indiisobutyl ether with a concentration of 2.1 mol/L was added dropwiseslowly over 4 hours while holding the temperature in the reactor at 20°C. After completion of the dropping, the mixture was stirred at 20° C.for 1 hour and then subjected to solid-liquid separation at roomtemperature, followed by washing with three portions of 70-L toluene.Subsequently, following removal of toluene so that the slurryconcentration became 0.4 kg/L, a liquid mixture of 8.9 mol of di-n-butylether and 274 mol of titanium tetrachloride was added. Then, 20.8 mol ofphthaloyl chloride was further added, followed by a reaction at 110° C.for 3 hours. After completion of the reaction, the reaction mixture waswashed with three portions of toluene at 95° C. Subsequently, the slurryconcentration was adjusted to 0.4 kg/L and then 3.13 mol of diisobutylphthalate, 8.9 mol of di-n-butyl ether and 109 mol of titaniumtetrachloride were added, followed by a reaction at 105° C. for 1 hour.After the completion of the reaction, the reaction mixture was subjectedto solid-liquid separation at that temperature, followed by washing withtwo portions of 90-L toluene at 95° C. Subsequently, the slurryconcentration was adjusted to 0.4 kg/L and then 8.9 mol of di-n-butylether and 109 mol of titanium tetrachloride were added, followed by areaction at 95° C. for 1 hour. After the completion of the reaction, thereaction mixture was subjected to solid-liquid separation at thattemperature, followed by washing with two portions of 90-L toluene atthe same temperature. Subsequently, the slurry concentration wasadjusted to 0.4 kg/L and then 8.9 mol of di-n-butyl ether and 109 mol oftitanium tetrachloride were added, followed by a reaction at 95° C. for1 hour. After completion of the reaction, the reaction mixture wassubjected to solid-liquid separation at that temperature. The resultingsolid was then washed with three portions of 90-L toluene at thattemperature and additionally with three portions of 90-L hexane, andthen dried under reduced pressure to yield 12.8 kg of a solid catalystcomponent. The solid catalyst component included 2.1% by weight oftitanium atoms, 18% by weight of magnesium atoms, 60% by weight ofchlorine atoms, 7.15% by weight of phthalic acid ester, 0.05% by weightof ethoxy groups, 0.26% by weight of butoxy groups. The componentincluded no fine powder and had a good powder property. This solidcatalyst component is hereinafter called solid catalyst component (II).

(3) Solid Catalyst Component (III)

A 200-L cylindrical reactor having a diameter of 0.5 m which wasequipped with a stirrer having three pairs of blades 0.35 m in diameterand also equipped with four baffle plates 0.05 m wide was purged withnitrogen. Into the reactor, 54 L of hexane, 100 g of diisobutylphthalate, 20.6 kg of tetraethoxy silane and 2.23 kg of tetrabutoxytitanium were charged and stirred. Then, to the stirred mixture, 51 L ofa solution of butylmagnesium chloride in di-n-butyl ether(concentration=2.1 mol/L) was dropped over 4 hour while the temperatureinside the reactor was held at 7° C. The stirring speed during thisoperation was 150 rpm. After the completion of the dropping, the mixturewas stirred at 20° C. for 1 hour and then was filtered. The resultingsolid was washed with three portions of 70-L of toluene at roomtemperature. Toluene was added to the solid to yield a solid catalystcomponent precursor slurry. The solid catalyst component precursorcontained 1.9% by weight of Ti, 35.6% by weight of OEt (ethoxy group),and 3.5% by weight of OBu (butoxy group). It had an average particlediameter of 39 μm and contained fine powder component with a diameter ofup to 16 μm in an amount of 0.5% by weight. Then, toluene was drained sothat the slurry volume became 49.7 L and the residue was stirred at 80°C. for 1 hour. After that, the slurry was cooled to a temperature of 40°C. or lower and a mixture of 30 L of titanium tetrachloride and 1.16 kgof di-n-butyl ether was added under stirring. Moreover, 4.23 kg oforthophthaloyl chloride was charged. After being stirred for 3 hours ata temperature inside the reactor of 110° C., the mixture was filteredand the resulting solid was washed with three portions of 90-L oftoluene at 95° C. Toluene was added to the solid to form a slurry, whichwas subsequently left stand. Toluene was then drained so that the slurryvolume became 49.7 L. Thereafter, a mixture of 15 L of titaniumtetrachloride, 1.16 kg of di-n-butyl ether and 0.87 kg of diisobutylphthalate was charged. After being stirred for 1 hour at a temperatureinside the reactor of 105° C., the mixture was filtered and theresulting solid was washed with two portions of 90-L of toluene at 95°C. Toluene was added to the solid to form a slurry, which was leftstand. Toluene was then drained so that the slurry volume became 49.7 L.Thereafter, a mixture of 15 L of titanium tetrachloride and 1.16 kg ofdibutyl ether was charged. After being stirred for 1 hour at atemperature inside the reactor of 105° C., the mixture was filtered andthe resulting solid was washed with two portions of 90-L of toluene at95° C. Toluene was added to the solid to form a slurry, which was leftstand. Toluene was then drained so that the slurry volume became 49.7 L.Thereafter, a mixture of 15 L of titanium tetrachloride and 1.16 kg ofdi-n-butyl ether was charged. After being stirred for 1 hour at atemperature inside the reactor of 105° C., the mixture was filtered andthe resulting solid was washed with three portions of 90-L of toluene at95° C. and two portions of 90-L of hexane. The resulting solid componentwas dried to yield a solid catalyst component. The solid catalystcomponent included 2.1% by weight of Ti and 10.8% by weight of phthalatecomponent. This solid catalyst component is hereinafter called solidcatalyst component (III).

(4) Solid Catalyst Component (IV)

A 200-L SUS reactor equipped with a stirrer was purged with nitrogen,and then 80 L of hexane, 6.55 mol of tetrabutoxytitanium, 2.8 mol ofdiisobutyl phthalate and 98.9 mol of tetraethoxysilane were fed to forma homogeneous solution. Then, 51 L of a butylmagnesium chloride solutionin diisobutyl ether at a concentration of 2.1 mol/L was dropped slowlyover 5 hours while the temperature inside the reactor was held at 5° C.After the dropping, the mixture was stirred at 5° C. for 1 hour and atroom temperature for additional 1 hour. Subsequently, the mixture wassubjected to solid-liquid separation at room temperature, followed bywashing with three portions of 70 L toluene. Then, the amount of toluenewas adjusted so that the slurry concentration became 0.2 kg/L and theresulting slurry was stirred at 105° C. for 1 hour. Then, the mixturewas cooled to 95° C. and 47.6 mol of diisobutyl phthalate was added,followed by a reaction at 95° C. for 30 minutes. After the reaction, thereaction mixture was subjected to solid-liquid separation, followed bywashing with two portions of toluene. Then, the amount of toluene wasadjusted so that the slurry concentration became 0.4 kg/L, 3.1 mol ofdiisobutyl phthalate, 8.9 mol of di-n-butyl ether and 274 mol oftitanium tetrachloride were added, followed by a reaction at 105° C. for3 hours. After the completion of the reaction, the reaction mixture wassubjected to solid-liquid separation at that temperature, followed bywashing with two portions of 90-L toluene at the same temperature. Theamount of toluene was adjusted so that the slurry concentration became0.4 kg/L, 8.9 mol of di-n-butyl ether and 137 mol of titaniumtetrachloride were added, followed by a reaction at 105° C. for 1 hour.After completion of the reaction, the reaction mixture was subjected tosolid-liquid separation at that temperature. The resulting solid wasthen washed with three portions of 90-L toluene at that temperature andadditionally with three portions of 70-L hexane, and then dried underreduced pressure to yield 11.4 kg of a solid catalyst component. Thesolid catalyst component included 1.83% by weight of titanium atom, 8.4%by weight of phthalate, 0.30% by weight of ethoxy groups and 0.20% byweight of butoxy groups. This solid catalyst component is hereinaftercalled solid catalyst component (IV).

[Polymerization to Polymer]

(1) Polymerization to Propylene Homopolymer (HPP)

(1-1) Polymerization to HPP-1

(1-1a) Preliminary Polymerization

In a 3-L SUS autoclave equipped with a stirrer, 25 mmol/L oftriethylaluminum (hereinafter abbreviated as TEA) andtert-butyl-n-propyldimethoxysilane (hereinafter abbreviated astBunPrDMS) as an electron-donating component in a tBunPrDMS-to-TEA ratioof 0.1 (mol/mol) and also 19.5 g/L of the solid catalyst component (III)were added to hexane which had been fully dehydrated and degassed.Subsequently, preliminary polymerization was carried out by feedingpropylene continuously until the amount of the propylene became 2.5 gper gram of the solid catalyst while keeping the temperature at 15° C.or lower. The resulting preliminary polymer slurry was transferred to a120-L SUS dilution tank with a stirrer, diluted by addition of a fullyrefined liquid butane, and preserved at a temperature of 10° C. orlower.

(1-1b) Main Polymerization

In a fluidized bed reactor having a capacity of 1 m³ and equipped with astirrer, propylene and hydrogen were fed so as to keep a polymerizationtemperature of 83° C., a polymerization pressure of 1.8 MPa and ahydrogen concentration in the vapor phase of 17.9 vol % relative topropylene. Continuous vapor phase polymerization was carried out whilecontinuously feeding 43 mmol/h of TEA, 6.3 mmol/h of tBunPrDMS and 1.80g/h of the preliminary polymer slurry prepared in (1-1a) as solidcatalyst components. Thus, 18.6 kg/h of polymer was obtained. Theresulting polymer had an intrinsic viscosity [η]_(P) of 0.78 dl/g, anisotactic pentad fraction of 0.985 and a molecular weight distributionof 4.3. The MFR was 280 g/10 min.

(1-2) Polymerization to HPP-2

(1-2a) Preliminary Polymerization

Preliminary polymerization was carried out in the same manner as in thepreparation of HPP-1.

(1-2b) Main Polymerization

Main polymerization was carried out in the same manner as in thepreparation of HPP-1 except the hydrogen concentration in the vaporphase and the amount of the solid catalyst component supplied wereadjusted. The resulting polymer had an intrinsic viscosity [η]_(P) of1.08 dl/g.

(1-3) Polymerization to HPP-3

(1-3a) Preliminary Polymerization

The preliminary polymerization was carried out in the same manner asHPP-1 except the solid catalyst component was changed to solid catalystcomponent (I).

(1-3b) Main Polymerization

Main polymerization was carried out in the same manner as in thepreparation of HPP-1 except the hydrogen concentration in the vaporphase and the amount of the solid catalyst component supplied wereadjusted. The resulting polymer had an intrinsic viscosity [η]_(P) of0.97 dl/g.

(1-4) Polymerization to HPP-4

(1-4a) Preliminary Polymerization

The preliminary polymerization was carried out in the same manner asHPP-1 except the solid catalyst component was changed to solid catalystcomponent (I).

(1-4b) Main Polymerization

Main polymerization was carried out in the same manner as in thepreparation of HPP-1 except the hydrogen concentration in the vaporphase and the amount of the solid catalyst component supplied wereadjusted. The resulting polymer had an intrinsic viscosity [η]_(P) of0.92 dl/g.

(1-5) Polymerization to HPP-5

(1-5a) Preliminary Polymerization

Preliminary polymerization was carried out in the same manner as HPP-1except the solid catalyst component was changed to solid catalystcomponent (IV) and the electron donor compound was changed tocyclohexylethyldimethoxysilane (hereinafter abbreviated as CHEDMS).

(1-5b) Main Polymerization

Main polymerization was carried out in the same manner as in thepreparation of HPP-1 except the hydrogen concentration in the vaporphase and the amount of the solid catalyst component supplied wereadjusted. The resulting polymer had an intrinsic viscosity [η]_(P) of1.45 dl/g.

(2) Preparation of Propylene-Ethylene Block Copolymer (BCPP)

(2-1) Preparation of BCPP

After a SUS loop-type reactor having a capacity of 0.36 m³ for liquidphase polymerization was purged fully with propylene, 0.105 mol/hr oftriethylaluminium and 0.0057 mol/hr oftert-butyl-n-propyl-dimethoxysilane were fed. Then, the innertemperature was adjusted to 45-55° C. and the pressure was adjusted to3.3-3.4 MPa with propylene and hydrogen, followed by continuous feedingof 0.040-0.050 kg/hr of solid catalyst component (III). Thus,polymerization was started. The polymer produced in the loop-typereactor for liquid phase polymerization was transferred to a vapor phasepolymerization reactor. The vapor phase polymerization reactor includedthree reactors. In a first reactor (capacity: 45.75 m³), production of apropylene homopolymer component by vapor phase polymerization wascontinued by continuously feeding propylene so as to keep the reactiontemperature at 70° C. and the reaction pressure at 1.9 MPa and feedinghydrogen so as to keep the hydrogen concentration in the vapor phase at17.5-18.5 vol %. Subsequently, the propylene homopolymer componentproduced in the first reactor was introduced into a second reactorintermittently. In the second reactor (capacity: 22.68 m³), a propylenehomopolymer component (hereinafter, referred to as polymer component(I)) was produced by continuing vapor phase polymerization whilecontinuously feeding propylene so as to keep the reaction temperature at70° C. and the reaction pressure at 1.5 MPa and feeding hydrogen so asto keep the hydrogen concentration in the vapor phase at 17.5-18.5 vol%. Subsequently, the propylene homopolymer component produced in thesecond reactor (polymer component (I)) was introduced into a thirdreactor intermittently. In the third reactor (capacity: 40.59 m³), vaporphase polymerization for producing an ethylene-propylene copolymercomponent (hereinafter, referred to as polymer component (II)) wascontinued by continuously feeding propylene so as to keep the reactiontemperature at 70° C. and the reaction pressure at 1.1 MPa, feedinghydrogen so as to keep the hydrogen concentration in the vapor phase at2.5-3.5 vol % and feeding ethylene so as to keep the ethyleneconcentration in the vapor phase at 24-25 vol %. Subsequently, a powdercomposed of polymer component (I) and polymer component (II) in thereactor (third reactor) was introduced into a deactivation vesselintermittently and the catalyst component was deactivated with water.Then, the powder was dried in nitrogen at 80° C. to yield a white powdercomposed of propylene-ethylene block copolymer.

The polymer component (I) produced in the second reactor was sampled ina small amount and was analyzed. The analysis revealed that the polymercomponent (I) had an intrinsic viscosity [η]_(I) of 0.90 dl/g and anisotactic pentad fraction of 0.983. The finally-producedpropylene-ethylene block copolymer had an intrinsic viscosity[η]_(total) of 1.34 dl/g. An analysis revealed that the content of apropylene-ethylene random copolymer (EP content) in thepropylene-ethylene block copolymer was 26.5% by weight. Therefore, thepropylene-ethylene random copolymer component (EP portion) produced inthe third reactor was found to have an intrinsic viscosity [η]_(EP) of2.6 dl/g. An analysis revealed that the ethylene content of the EPportion was 41% by weight. The results of the analysis of the resultingpolymer are shown in Table 1.

(2-2) Preparation of BCPP-2

Polymerization was carried out in the same manner as in the preparationof BCPP-1 except the hydrogen concentration and the ethyleneconcentration in the vapor phase and the amount of the solid catalystcomponent supplied were adjusted so that a polymer given in Table 2 wasproduced. The results of the analysis of the resulting polymer are shownin Table 1.

(2-3) Preparation of BCPP-3

Polymerization was carried out in the same manner as in the preparationof BCPP-1 except the hydrogen concentration and the ethyleneconcentration in the vapor phase and the amount of the solid catalystcomponent supplied were adjusted so that a polymer given in Table 2 wasproduced. The results of the analysis of the resulting polymer are shownin Table 1.

(2-4) Preparation of BCPP-4

(2-4a) Preliminary Polymerization

In a 3-L SUS autoclave equipped with a stirrer, 20 mmol/L of TEA,tBunPrDMS as an electron donor component, wherein tBunPrDMS/TEA=0.1(mol/mol), and 20 g/L of solid catalyst component (II) were added tohexane which had been fully dewatered and degassed. Subsequently, apreliminary polymerization was carried out by feeding propylenecontinuously until the amount of the propylene became 2.5 g per gram ofthe solid catalyst while the temperature was kept at 15° C. or lower.The resulting preliminary polymer slurry was transferred to a 200-L SUSdilution tank equipped with a stirrer, diluted by addition of a fullyrefined liquid butane, and stored at a temperature of 10° C. or lower.

(2-4b) Main Polymerization

Two fluidized bed reactors each having a capacity of 1 m³ equipped witha stirrer were placed in series. Main polymerization was carried out byvapor phase polymerization in which a propylene polymer portion wasproduced by polymerization in a first reactor and then was transferredcontinuously to a second reactor without being deactivated and apropylene-ethylene copolymer portion was produced continuously bypolymerization in the second reactor.

In the first reactor for the former stage, propylene and hydrogen werefed so as to keep a polymerization temperature of 80° C., apolymerization pressure of 1.8 MPa and a hydrogen concentration in thevapor phase of 10 vol %. Under such conditions, continuouspolymerization was carried out while 20 mmol/h of TEA, 4.0 mmol/h oftBunPrDMS and 0.7 g/h of the preliminary polymer slurry prepared in(2-4a) as a solid catalyst component were fed, affording 13.2 kg/h ofpolymer. The polymer had an intrinsic viscosity [η]_(P) of 0.95 dl/g.The discharged polymer was fed continuously to the second reactor to thelatter step without being deactivated. In the second reactor, propylene,ethylene and hydrogen were continuously fed so as to keep apolymerization temperature of 65° C., a polymerization pressure of 1.4MPa, a hydrogen concentration in the vapor phase of 2.5 vol % and anethylene concentration of 24.1 vol %. Under such conditions, acontinuous polymerization was continued while 6.2 mmol/h oftetraethoxysilane (hereinafter abbreviated as TES) was fed. Thus, 19.4kg/h of polymer was obtained. The resulting polymer had an intrinsicviscosity [η]_(T) of 5 dl/g and the polymer content (EP content) in theportion produced in the latter step was 27% by weight. Therefore, thepolymer produced in the latter step portion (EP portion) had anintrinsic viscosity [η]_(EP) of 3.0 dl/g. An analysis revealed that theethylene content of the EP portion was 41% by weight. The results of theanalysis of the resulting polymer are shown in Table 1.

(2-5) Preparation of BCPP-5

(2-5a) Preliminary Polymerization

Into a jacketed SUS reactor with a capacity of 3 m³, n-hexane which hadbeen degassed and dewatered, solid catalyst component (IV),cyclohexylethyldimethoxysilane (B) and triethylaluminium (C) wereintroduced so that C/A=1.67 mmol/g and B/C=0.13 mmol/mmol. Thus, aprepolymerization catalyst component was prepared so that the degree ofprepolymerization with propylene became 3.5 (g/prepolymer/g-solidcatalyst component (IV)).

(2-5b) Main Polymerization

In a jacketed SUS reactor (first reactor) with a capacity of 248 m³,vapor phase polymerization for producing a powdery propylene homopolymercomponent (hereinafter, referred to as polymer component (I)) wascarried out continuously while the prepolymerization catalyst componentprepared in the aforementioned prepolymerization and propylene were fedcontinuously under conditions where the reaction temperature and thereaction pressure were kept at 83° C. and 2.1 MPa, respectively, andhydrogen was fed so as to keep the hydrogen concentration in the vaporphase at 3.7 vol %. Subsequently, some part of the polymer component (I)was transferred intermittently into a jacketed SUS reactor (secondreactor) with a capacity of 115 m³. Production of polymer component (I)by vapor phase polymerization was continued by feeding propylenecontinuously under conditions where the reaction temperature and thereaction pressure were kept at 83° C. and 1.7 MPa, respectively, andhydrogen was fed so as to keep the hydrogen concentration in the vaporphase at 3.6 vol %. The polymer component (I) produced by thepolymerization in the second reactor was sampled and analyzed. Theanalysis revealed that it had an intrinsic viscosity [η]_(I) of 1.07dl/g and an isotactic pentad fraction of 0.970.

Subsequently, a part of the polymer component (I) produced in the secondreactor was transferred to a jacketed SUS reactor (third reactor) with acapacity of 219 m³ and then production of a propylene-ethylene randomcopolymer component (hereinafter, referred to as polymer component (II))by polymerization of propylene and ethylene was started. The vapor phasepolymerization for producing polymer component (II) was continued whilepropylene and ethylene were fed continuously at a weight proportion ofpropylene/ethylene=2/1 so that the reaction pressure was kept at 1.3 MPaat a reaction temperature of 70° C. and the hydrogen concentration inthe vapor phase was adjusted so as to be kept at 2.3 vol %.

Subsequently, a powder composed of polymer component (I) and polymercomponent (II) in the reactor (third reactor) was introduced into adeactivation vessel intermittently and the catalyst component wasdeactivated with water. Then, the powder was dried in nitrogen at 65° C.to yield a white powder composed of propylene-ethylene block copolymer.

The finally-produced propylene-ethylene block copolymer had an intrinsicviscosity [η]_(T) of 1.4 dl/g. An analysis revealed that the content ofa propylene-ethylene random copolymer (EP content) in thepropylene-ethylene block copolymer was 21% by weight. Therefore, thepropylene-ethylene random copolymer component (EP portion) produced inthe third reactor was found to have an intrinsic viscosity [η]_(EP) of2.6 dl/g. An analysis revealed that the ethylene content of the EPportion was 40% by weight. The results of the analysis of the resultingpolymer are shown in Table 1.

(2-6) Preparation of BCPP-6

Five SUS reactors having a capacity of 45 or 32 m³ equipped with astirrer and a jacket were fully purged with propylene. The pressure inthe first reactor was adjusted to 0.5 kgf/cm² with propylene and 20 m³of n-heptane was charged. After starting the stirrer, 50 mol oftriethylaluminum was fed and the temperature in the reactor was raisedto 60-75° C. Subsequently, the reaction pressure was increased to 4-8kgf/cm² with propylene. Hydrogen was fed so that the hydrogenconcentration was kept at 15-17% and then solid catalyst component (I)was fed to start polymerization. At the same time, feeding of 2.5-3.0kg/hr (about 24-25 mol/hr) of triethylaluminium was started. After thestart of the reaction, the reaction pressure was increased to anintended level, namely 4.5-9.0 kgf/cm², while the stability in thereactor was checked. The polymerization was continued while propyleneand hydrogen were supplied so that the hydrogen concentration in thevapor phase was kept to 19-21%. The resulting polymer slurry wasdischarged to the next reactor and was subjected to polymerizationcontinuously under predetermined conditions. In the five reactorsarranged in series, production of polypropylene portion (hereinafter,referred to as “P portion”) by polymerization was continued. The Pportion was sampled and analyzed. The P portion had an intrinsicviscosity [η]_(P) of 0.80 dl/g.

The reaction pressure in the sixth through eighth reactors wereincreased to 2-4 kgf/cm² with propylene and ethylene, and polymerizationof an ethylene-propylene copolymer portion (hereinafter, referred to asEP portion) was started. While the reaction pressure was kept to 2-4kgf/cm² at a reaction temperature of 52° C., propylene/ethylene mixedgas was supplied continuously so that the hydrogen concentration in thevapor phase was kept to 0.05 to 0.2%. Thus, the polymerization of the EPportion was continued. The resulting polymer slurry was discharged tothe next reactor and was subjected to polymerization continuously underpredetermined conditions. Polymerization of the EP portion was continuedin the three reactors arranged in series. When transfer of the polymerslurry in the reactor to a deactivation vessel was started, introductionof 1.0-1.5 kg/hr (about 7-8 mol/hr) oftert-butyl-n-propyldimethoxysilane into the reactor was started.

The overall polymer slurry in the reactors was transferred to adeactivation vessel. The unreacted monomer was separated anddeactivation treatment with water was conducted. Then, the polymerslurry was subjected to centrifugal separation to collect solid polymer,which was then dried in a drier. Thus, a white powder was obtained.

The finally-produced propylene-ethylene block copolymer had an intrinsicviscosity [η]_(T) of 1.42 dl/g. An analysis revealed that the content ofa propylene-ethylene random copolymer (EP content) in thepropylene-ethylene block copolymer was 10% by weight. Therefore, thepropylene-ethylene random copolymer component (EP portion) produced inthe third reactor was found to have an intrinsic viscosity [η]_(EP) of7.0 dl/g. An analysis revealed that the EP portion had an ethylenecontent of 40% by weight and an isotactic pentad fraction of 0.991. Theresults of the analysis of the resulting polymer are shown in Table 1.

(2-7) Preparation of BCPP-7

Polymerization was carried out in the same manner as in the preparationof BCPP-4 except the hydrogen concentration and the ethyleneconcentration in the vapor phase and the amount of the solid catalystcomponent supplied were adjusted so that a polymer given in Table 1 wasproduced. The results of the analysis of the resulting polymer are shownin Table 1.

The values of [η]_(P), [η]_(EP), ethylene content in an EP and EPcontent shown in Table 1 are values obtained by analysis of the powdersof the propylene-ethylene block copolymer powders (BCPP-1 throughBCPP-6) produced by the above-described polymerizations. Each MFR shownin Table 1 is an MFR of pellets produced by pelletization of a mixtureprepared by adding 0.05 parts by weight of calcium stearate(manufactured by NOF Corp.) as a stabilizer, 0.05 parts by weight of3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane(Sumilizer GA80, manufactured by Sumitomo Chemical Co., Ltd.) and 0.05parts by weight of bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite (Ultranox U626, manufactured by GE Specialty Chemicals) to100 parts by weight of a powder by means of an extruder.

(2-7) Preparation of BCPP-8

A powder (masterbatch) composed of a polyolefin resin powder impregnatedwith 2,5-dimethyl-2,5-di(tert-butylperoxyl)hexane as peroxide was mixedwith AZ564G manufactured by The Polyolefin Company and the resultingmixture was subjected to decomposition treatment in an extruder. The MFRwas 65 g/10 min. An analysis revealed that the propylene-ethylene randomcopolymer content (EP content) was 22% by weight. The ethylene contentin the EP portion was 46% by weight and the isotactic pentad fractionwas 0.970. The intrinsic viscosity of the component soluble in 20° C.xylene, which corresponds to the intrinsic viscosity [η]_(EP) of thepropylene-ethylene random copolymer portion, was 1.6 dl/g.

Example 1

To 100 parts by weight of a propylene-ethylene block copolymer powder(BCPP-1), 0.05 part by weight of calcium stearate (manufactured by NOFCorp.), 0.05 part by weight of3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane(Sumilizer GA80, manufactured by Sumitomo Chemical Co., Ltd.), and 0.05parts by weight of bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite (Ultranox U626, manufactured by GE Specialty Chemicals) wereadded as stabilizers and dry blended. The resulting mixture waspelletized by means of an extruder.

A polypropylene resin composition was prepared by blending 28% by weightof BCPP-1 pellets, 31% by weight of a powder of a propylene homopolymer(HPP-4), ethylene-butene-1 random copolymer rubbers as ethylene-α-olefincopolymer rubber (B), namely 3.5% by weight of EBR-1 (EBM3011Pmanufactured by JSR Corp., density: 0.860 g/cm³, MFR (230° C., 2.16 kgfload): 0.26 g/10 min) and 4% by weight of EBR-2 (TAFMER A0550manufactured by Mitsui Chemicals, Inc., density: 0.861 g/cm³, MFR (230°C., 2.16 kgf load): 0.94 g/10 min), an ethylene-octene-1 randomcopolymer rubber as ethylene-α-olefin copolymer rubber (C), namely 11.5%by weight of EOR-2 (Engage 8842 supplied by DuPont Dow Elastomers JapanLLC, density: 0.857 g/cm³, MFR (230° C., 2.16 kgf load): 2.7 g/10 min),and 22% by weight of talc having an average particle diameter of 2.7 μm(manufactured by Hayashi Kasei Co., Ltd., commercial name: MWHST) asinorganic filler (D), preliminarily mixing the blend uniformly in atumbler, and then kneading and extruding the resulting mixture using atwin screw extruder (TEX44SS-30BW-2V, manufactured by The Japan SteelWorks, Ltd.) at an extrusion rate of 50 kg/hr, 230° C. and a screw speedof 350 rpm.

In Table 2, the compounding amounts of the components, the MFR and theresults of evaluation of physical properties and weld line condition ofan injection molded article are shown.

Example 2

Treatment the same as that of Example 1 was carried out by using apropylene-ethylene block copolymer (BCPP) shown in Table 2. The MFR ofthe resulting resin composition and physical properties of an injectionmolded article were measured and the weld line condition of an injectionmolded article was evaluated. Evaluation results are shown in Table 2.

Examples 3-5

Treatment the same as that of Example 1 was carried out by using apropylene-ethylene block copolymer (BCPP) shown in Table 2 and blending9% by weight of an ethylene-butene-1 random copolymer rubber EBR-3(TAFMER A0250 manufactured by Mitsui Chemicals, Inc., density: 0.861g/cm³, MFR (230° C., 2.16 kgf load): 0.46 g/10 min) as ethylene-α-olefincopolymer rubber (B), 10% by weight of an ethylene-octene-1 randomcopolymer rubber EOR-2 (Engage 8842 supplied by DuPont Dow ElastomersJapan LLC, density: 0.857 g/cm³, MFR (230° C., 2.16 kgf load) : 2.7 g/10min) as ethylene-α-olefin copolymer rubber (C), and 21.3% by weight oftalc having an average particle diameter of 2.7 μm (manufactured byHayashi Kasei Co., Ltd., commercial name: MWHST) as inorganic filler(D). The MFR of the resulting resin composition and physical propertiesof an injection molded article were measured and the weld line conditionof an injection molded article was evaluated. Evaluation results areshown in Table 2.

Comparative Example 1

Treatment the same as that of Example 1 was carried out by using apropylene-ethylene block copolymer (BCPP) shown in Table 3 and blending10.5% by weight of an ethylene-butene-1 random copolymer rubber EBR-4(ENR7467 manufactured by DuPont Dow Elastomers Japan LLC, density: 0.862g/cm³, MFR (230° C., 2.16 kgf load): 2.5 g/10 min), 10% by weight of anethylene-octene-1 random copolymer rubber EOR-2 (Engage 8842 supplied byDuPont Dow Elastomers Japan LLC, density: 0.857 g/cm³, MFR (230° C.,2.16 kgf load) : 2.7 g/10 min) as ethylene-α-olefin copolymer rubber(C), and 21.3% by weight of talc having an average particle diameter of2.7 μm (manufactured by Hayashi Kasei Co., Ltd., commercial name: MWHST)as inorganic filler (D). The MFR of the resulting resin composition andphysical properties of an injection molded article were measured and theweld line condition of an injection molded article was evaluated.Evaluation results are shown in Table 3.

Comparative Example 2

Treatment the same as that of Example 3 was carried out by using apropylene-ethylene block copolymer (BCPP) and a propylene homopolymer(HPP) shown in Table 3. The MFR of the resulting resin composition andphysical properties of an injection molded article were measured and theweld line condition of an injection molded article was evaluated.Evaluation results are shown in Table 3.

Comparative Example 3

Treatment the same as that of Example 1 was carried out by using apropylene-ethylene block copolymer (BCPP) and a propylene homopolymer(HPP) shown in Table 3 and blending 3.5% by weight of anethylene-propylene-diene random copolymer rubber EPDM-1 (EP57Pmanufactured by JSR Corp., density: 0.860 g/cm³, MFR (230° C., 2.16 kgfload): 0.08 g/10 min), 4% by weight of an ethylene-octene-1 randomcopolymer rubber EOR-1 (Engage 8150 supplied by DuPont Dow ElastomersJapan LLC, density: 0.868 g/cm³, MFR (230° C., 2.16 kgf load) : 1.1 g/10min), 11% by weight of an ethylene-octene-1 random copolymer rubberEOR-2 (Engage 8842 supplied by DuPont Dow Elastomers Japan LLC, density:0.857 g/cm³, MFR (230° C., 2.16 kgf load): 2.7 g/10 min), and 22% byweight of talc having an average particle diameter of 2.7 μm(manufactured by Hayashi Kasei Co., Ltd., commercial name: MWHST) asinorganic filler (D). The MFR of the resulting resin composition andphysical properties of an injection molded article were measured and theweld line condition of an injection molded article was evaluated.Evaluation results are shown in Table 3.

Comparative Examples 4 and 5

Treatment the same as that of Comparative Example 3 was carried out byusing a propylene-ethylene block copolymer (BCPP) and a propylenehomopolymer (HPP) shown in Table 3 and changing the amount of EOR-2 to12% by weight. The MFR of the resulting resin composition and physicalproperties of an injection molded article were measured and the weldline condition of an injection molded article was evaluated. Evaluationresults are shown in Table 3.

Comparative Example 6

Treatment the same as that of Example 1 was carried out by using 19% byweight of an ethylene-butene-1 random copolymer rubber EBR-3 (TAFMERA0250 manufactured by Mitsui Industries, Inc., density: 0.861 g/cm³, MFR(230° C., 2.16 kgf load): 0.46 g/10 min) as ethylene-α-olefin copolymerrubber (B) and adding no ethylene-α-olefin copolymer rubber (C). The MFRof the resulting resin composition and physical properties of aninjection molded article were measured and the weld line condition of aninjection molded article was evaluated. Evaluation results are shown inTable 4.

Comparative Example 7

Treatment the same as that of Example 1 was carried out by using 7.5% byweight of an ethylene-butene-1 random copolymer rubber EBR-3 (TAFMERA0250 manufactured by Mitsui Industries, Inc., density: 0.861 g/cm³, MFR(230° C., 2.16 kgf load): 0.46 g/10 min) and 11.5% by weight of anethylene-butene-1 random copolymer rubber EBR-5 (EXCELLEN FX, CX5505manufactured by Sumitomo Chemical Co., Ltd., density: 0.870 g/cm³, MFR(230° C., 2.16 kgf load): 27.6 g/10 min) as ethylene-α-olefin copolymerrubber (B). The MFR of the resulting resin composition and physicalproperties of an injection molded article were measured and the weldline condition of an injection molded article was evaluated. Evaluationresults are shown in Table 4.

TABLE 1 Propylene-ethylene block copolymer unit BCPP-1 BCPP-2 BCPP-3BCPP-4 BCPP-5 BCPP-6 BCPP-7 [η]P dl/g 0.90 0.97 0.90 0.95 1.07 0.80 0.93[η]EP dl/g 2.6 2.3 2.3 3.0 2.6 7.0 2.5 (C′2)EP wt % 41 48 47 41 40 40 30EP content wt % 27 26 26 27 21 10 25 MFR g/10 min 36 31 45 25 30 86 25[mmmm] 0.983 0.988 0.984 0.97 0.991

TABLE 2 Exam- Exam- Exam- Exam- Exam- unit ple 1 ple 2 ple 3 ple 4 ple 5BCPP-1 wt % 28 14 BCPP-2 wt % 14 25 BCPP-3 wt % 5 5 BCPP-4 wt % 23 28HPP-2 wt % 9 HPP-4 wt % 31 31 29.7 31.7 22.7 EBR-1 wt % 3.5 3.5 EBR-2 wt% 4 4 EBR-3 wt % 9 9 9 EOR-2 wt % 11.5 11.5 10 10 10 Talc 22 22 21.321.3 21.3 MFR g/10 39 33 31 31 28 min UE % 398 471 465 483 >500 FM MPa1987 1965 1947 1952 1978 IZOD23° C. kJ/m² 42 39 39 43 48 IZOD−30° C.kJ/m² 5.4 5.9 6.3 6.3 6.3 HDT ° C. 65 66 66 67 66 HR R 62 58 59 62 62scale BP ° C. −22 −25 −28 −26 −25 Length of mm 105 125 110 103 95 weldline Notice- ∘ ∘ ∘ ∘ ∘ ability of weld line *1) *1) Noticeability ofweld line ∘: There was no noticeable weld line. x: There was anoticeable weld line.

TABLE 3 Comparative Comparative Comparative Comparative Comparative unitExample 1 Example 2 Example 3 Example 4 Example 5 BCPP-1 wt % 28 BCPP-5wt % 14.5 BCPP-6 wt % 40 BCPP-7 wt % 30 BCPP-8 wt % 35 32 HPP-1 wt % 1212 HPP-2 wt % 7 HPP-3 wt % 14.5 16.5 HPP-4 wt % 17.7 31.5 HPP-5 wt % 3EBR-3 wt % 9 EBR-4 wt % 10.5 EPDM-1 wt % 3.5 3.5 3.5 EOR-1 wt % 4 4 4EOR-2 wt % 10 10 11 12 12 Talc wt % 22 21.3 22 22 22 MFR g/10 min 33 3739 45 30 UE % >500 277 366 156 >500 FM MPa 1928 1887 1982 1926 1763IZOD23° C. kJ/m² 50 31 34 20 55 IZOD−30° C. kJ/m² 5.1 5.4 4.9 4.8 5.0HDT ° C. 65 64 67 65 65 HR R scale 59 59 64 60 59 BP ° C. −21 −24 −21−21 −24 Length of weld line mm 145 110 115 95 91 Noticeability of x ∘ ∘∘ ∘ weld line *1) *1) Noticeability of weld line ∘: There was nonoticeable weld line. x: There was a noticeable weld line.

TABLE 4 Comparative Comparative Example 6 Example 7 BCPP-1 wt % 28BCPP-3 wt % 28 HPP-4 wt % 31 31 EBR-3 wt % 19 7.5 EBR-5 wt % 11.5 Talcwt % 22 22 MFR g/10 min 33 47 UE % 126 186 FM MPa 2024 1988 IZOD23° C.KJ/m² 29 25 IZOD−30° C. KJ/m² 5.2 4.4 HDT ° C. 67 65 HR R scale 61 60 BP° C. −23 −12 Length of weld mm 105 125 line Noticeability ∘ ∘ of weldline *1) *1) Noticeability of weld line ∘: There was no noticeable weldline. x: There was a noticeable weld line.

The polypropylene resin compositions of Examples 1-5 were superior influidity. Molded articles made from these compositions had no noticeableweld lines and had good balance between rigidity and impact resistance.

In a molded article of Comparative Example 1, in which the intrinsicviscosity [η]_(EP) of the propylene-ethylene random copolymer portion ofthe polypropylene resin does not satisfy a requirement of the presentinvention and no ethylene-α-olefin copolymer rubber (B) was included,there is a noticeable weld line.

A molded article of Comparative Example 2, in which the intrinsicviscosity [η]_(EP) of the propylene-ethylene random copolymer portion ofthe polypropylene resin does not satisfy a requirement of the presentinvention, does not have satisfactory balance among rigidity, toughnessand impact resistance.

A molded article of Comparative Example 3, in which theethylene-α-olefin copolymer rubber (B) does not satisfy a requirement ofthe present invention, does not have satisfactory balance amongrigidity, toughness and impact resistance.

A molded article of Comparative Example 4, in which the intrinsicviscosity [η]_(EP) of the propylene-ethylene random copolymer portion ofthe polypropylene resin does not satisfy a requirement of the presentinvention and the ethylene-α-olefin copolymer rubber (B) does notsatisfy a requirement of the present invention, does not havesatisfactory balance among rigidity, toughness and impact resistance.

A molded article of Comparative Example 5, in which the weight ratio ofpropylene units to ethylene units included in the propylene-ethylenerandom copolymer portion of the polypropylene resin does not satisfy arequirement of the present invention and the ethylene-α-olefin copolymerrubber (B) does not satisfy a requirement of the present invention, doesnot have satisfactory balance among rigidity, toughness and impactresistance.

Molded articles of Comparative Examples 6 and 7, in which theethylene-α-olefin copolymer rubber (C) does not satisfy a requirement ofthe present invention, does not have satisfactory balance amongrigidity, toughness and impact resistance.

The polypropylene resin composition of the present invention can be usedin applications in which a high quality is demanded such as automotiveinterior or exterior components.

1. A polypropylene resin composition comprising: from 50 to 93% byweight of a polypropylene resin (A), from 1 to 25% by weight of anethylene-α-olefin copolymer rubber (B) which includes units of anα-olefin having from 4 to 12 carbon atoms and ethylene units and has adensity of from 0.850 to 0.870 g/cm³ and a melt flow rate, as measuredat a temperature of 230° C. and a load of 2.16 kgf, of from 0.05 to 1g/10 min, from 1 to 25% by weight of an ethylene-α-olefin copolymerrubber (C) which includes units of an α-olefin having from 4 to 12carbon atoms and ethylene units and has a density of from 0.850 to 0.870g/cm³ and a melt flow rate, as measured at a temperature of 230° C. anda load of 2.16 kgf, of from 2 to 20 g/10 min, and from 5 to 25% byweight of an inorganic filler (D), provided that the overall amount ofthe polypropylene resin composition is 100% by weight, wherein thepolypropylene resin (A) is a propylene-ethylene block copolymer (A-1)satisfying requirements (1), (2), (3) and (4) defined below or a polymermixture (A-3) comprising the block copolymer (A-1) and a propylenehomopolymer (A-2), requirement (1): the block copolymer (A-1) is apropylene-ethylene block copolymer comprising from 55 to 90% by weightof a polypropylene portion and from 10 to 45% by weight of apropylene-ethylene random copolymer portion, provided that the overallamount of the block copolymer (A-1) is 100% by weight, requirement (2):the polypropylene portion of the block copolymer (A-1) is a propylenehomopolymer or a copolymer comprising propylene units and 1 mol % orless of units of a comonomer selected from the group consisting ofethylene and α-olefin having 4 or more carbon atoms, provided that theoverall amount of units constituting the copolymer is 100 mol %,requirement (3): the weight ratio of the propylene units to the ethyleneunits in the propylene-ethylene random copolymer portion of the blockcopolymer (A-1) is from 65/35 to 52/48, requirement (4): thepropylene-ethylene random copolymer portion of the block copolymer (A-1)has an intrinsic viscosity [η]_(EP-A) of not less than 2.2 dl/g but lessthan 4 dl/g.
 2. The polypropylene resin composition according to claim1, wherein the ratio of the content in weight of the ethylene-α-olefincopolymer rubber (B) to the content in weight of the ethylene-α-olefincopolymer rubber (C) is from 15/85 to 85/15.
 3. The polypropylene resincomposition according to claim 1, wherein the polypropylene portion ofthe block copolymer (A-1) has an intrinsic viscosity [η]_(P) of from 0.7dl/g to 1.3 dl/g and a molecular weight distribution, as measured byGPC, of not less than 3 but less than
 7. 4. The polypropylene resincomposition according to claim 1, wherein the polypropylene portion ofthe block copolymer (A-1) has an isotactic pentad fraction of 0.97 ormore.
 5. The polypropylene resin composition according to claim 1,wherein the inorganic filler (D) is talc.
 6. The polypropylene resincomposition according to claim 2, wherein the inorganic filler (D) istalc.
 7. The polypropylene resin composition according to claim 3,wherein the inorganic filler (D) is talc.
 8. The polypropylene resincomposition according to claim 4, wherein the inorganic filler (D) istalc.
 9. An injection-molded article made from the polypropylene resincomposition according to claim
 1. 10. An injection molded article madefrom the polypropylene resin composition according to claim
 2. 11. Aninjection molded article made from the polypropylene resin compositionaccording to claim
 3. 12. An injection molded article made from thepolypropylene resin composition according to claim
 4. 13. An injectionmolded article made from the polypropylene resin composition accordingto claim
 5. 14. An injection molded article made from the polypropyleneresin composition according to claim
 6. 15. An injection molded articlemade from the polypropylene resin composition according to claim
 7. 16.An injection molded article made from the polypropylene resincomposition according to claim 8.